Method and apparatus for providing dynamic multi-stage signal amplification in a medical device

ABSTRACT

Methods and apparatus for providing multi-stage signal amplification in a medical telemetry system are provided.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/209,741 filed Jul. 13, 2016, now U.S. Pat. No. 9,743,866,which is a continuation of U.S. patent application Ser. No. 14/596,759filed Jan. 14, 2015, now U.S. Pat. No. 9,402,584, which is acontinuation of U.S. patent application Ser. No. 14/188,659 filed Feb.24, 2014, now U.S. Pat. No. 8,937,540, which is a continuation of U.S.patent application Ser. No. 13/867,948 filed Apr. 22, 2013, now U.S.Pat. No. 8,698,615, which is a continuation of U.S. patent applicationSer. No. 13/437,894 filed Apr. 2, 2012, now U.S. Pat. No. 8,427,298,which is a continuation of U.S. patent application Ser. No. 13/114,029filed May 23, 2011, now U.S. Pat. No. 8,149,103, which is a continuationof U.S. patent application Ser. No. 12/849,004 filed Aug. 2, 2010, nowU.S. Pat. No. 7,948,369, which is a continuation of U.S. patentapplication Ser. No. 12/102,836 filed Apr. 14, 2008, now U.S. Pat. No.7,768,387, which claims priority under § 35 U.S.C. 119(e) to U.S.Provisional Application No. 60/911,866 filed Apr. 14, 2007, entitled“Method and Apparatus for Providing Dynamic Multi-Stage SignalAmplification in a Medical Device”, the disclosures of each of which areincorporated herein by reference for all purposes.

BACKGROUND

Analyte (e.g., glucose) monitoring systems including continuous anddiscrete monitoring systems generally include a small, lightweightbattery powered and microprocessor controlled system which is configuredto detect signals proportional to the corresponding measured glucoselevels using an electrometer, and RF signals to transmit the collecteddata. One aspect of certain analyte monitoring systems include atranscutaneous or subcutaneous analyte sensor configuration which is,for example, partially mounted on the skin of a subject whose analytelevel is to be monitored. The sensor cell may use a two orthree-electrode (work, reference and counter electrodes) configurationdriven by a controlled potential (potentiostat) analog circuit connectedthrough a contact system.

The analyte sensor may be configured so that a portion thereof is placedunder the skin of the patient so as to detect the analyte levels of thepatient, and another portion of segment of the analyte sensor that is incommunication with the transmitter unit. The transmitter unit isconfigured to transmit the analyte levels detected by the sensor over awireless communication link such as an RF (radio frequency)communication link to a receiver/monitor unit. The receiver/monitor unitperforms data analysis, among others on the received analyte levels togenerate information pertaining to the monitored analyte levels. Toprovide flexibility in analyte sensor manufacturing and/or design, amongothers, tolerance of a larger range of the analyte sensor sensitivitiesfor processing by the transmitter unit is desirable.

In view of the foregoing, it would be desirable to have a method andapparatus for providing a dynamic multi-stage amplification of signalsfor use in medical telemetry systems such as, for example, analytemonitoring systems.

SUMMARY OF THE INVENTION

In one embodiment, an apparatus including a first amplifier having atleast one input terminal and an output terminal, the at least one inputterminal coupled to a signal source, the output terminal configured toprovide a first output signal, a second amplifier having at least oneinput terminal and an output terminal, the at least one input terminalcoupled to the output terminal of the first amplifier, the outputterminal of the second amplifier configured to provide a second outputsignal, a processor operatively coupled to receive the first outputsignal and the second output signal, where the first output signal is apredetermined ratio of the second output signal, and further, where thefirst output signal and the second output signal are associated with amonitored analyte level of a user is disclosed.

These and other objects, features and advantages of the presentinvention will become more fully apparent from the following detaileddescription of the embodiments, the appended claims and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of a data monitoring and managementsystem for practicing one or more embodiments of the present invention;

FIG. 2 is a block diagram of the transmitter unit of the data monitoringand management system shown in FIG. 1 in accordance with one embodimentof the present invention;

FIG. 3 is a block diagram of the receiver/monitor unit of the datamonitoring and management system shown in FIG. 1 in accordance with oneembodiment of the present invention; and

FIG. 4 is a schematic of the dynamic multi-stage signal amplification inthe transmitter unit of the data monitoring and management system shownin FIG. 1 in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

As described in further detail below, in accordance with the variousembodiments of the present invention, there is provided a method andapparatus for providing dynamic multi-stage signal amplification for usein a medical telemetry system. In particular, within the scope of thepresent invention, there are provided method and apparatus for amulti-stage signal amplifier configuration in the analog interface ofthe data transmitter unit in the data processing and management system.

FIG. 1 illustrates a data monitoring and management system such as, forexample, analyte (e.g., glucose) monitoring system 100 in accordancewith one embodiment of the present invention. The subject invention isfurther described primarily with respect to a glucose monitoring systemfor convenience and such description is in no way intended to limit thescope of the invention. It is to be understood that the analytemonitoring system may be configured to monitor a variety of analytes,e.g., lactate, and the like.

Analytes that may be monitored include, for example, acetyl choline,amylase, bilirubin, cholesterol, chorionic gonadotropin, creatine kinase(e.g., CK-MB), creatine, DNA, fructosamine, glucose, glutamine, growthhormones, hormones, ketones, lactate, peroxide, prostate-specificantigen, prothrombin, RNA, thyroid stimulating hormone, and troponin.The concentration of drugs, such as, for example, antibiotics (e.g.,gentamicin, vancomycin, and the like), digitoxin, digoxin, drugs ofabuse, theophylline, and warfarin, may also be monitored.

The analyte monitoring system 100 includes a sensor 101, a transmitterunit 102 coupled to the sensor 101, and a primary receiver unit 104which is configured to communicate with the transmitter unit 102 via acommunication link 103. The primary receiver unit 104 may be furtherconfigured to transmit data to a data processing terminal 105 forevaluating the data received by the primary receiver unit 104. Moreover,the data processing terminal in one embodiment may be configured toreceive data directly from the transmitter unit 102 via a communicationlink which may optionally be configured for bi-directionalcommunication.

Also shown in FIG. 1 is a secondary receiver unit 106 which isoperatively coupled to the communication link and configured to receivedata transmitted from the transmitter unit 102. Moreover, as shown inthe Figure, the secondary receiver unit 106 is configured to communicatewith the primary receiver unit 104 as well as the data processingterminal 105. Indeed, the secondary receiver unit 106 may be configuredfor bi-directional wireless communication with each of the primaryreceiver unit 104 and the data processing terminal 105. As discussed infurther detail below, in one embodiment of the present invention, thesecondary receiver unit 106 may be configured to include a limitednumber of functions and features as compared with the primary receiverunit 104. As such, the secondary receiver unit 106 may be configuredsubstantially in a smaller compact housing or embodied in a device suchas a wrist watch, for example. Alternatively, the secondary receiverunit 106 may be configured with the same or substantially similarfunctionality as the primary receiver unit 104, and may be configured tobe used in conjunction with a docking cradle unit for placement bybedside, for night time monitoring, and/or bi-directional communicationdevice.

Only one sensor 101, transmitter unit 102, communication link 103, anddata processing terminal 105 are shown in the embodiment of the analytemonitoring system 100 illustrated in FIG. 1. However, it will beappreciated by one of ordinary skill in the art that the analytemonitoring system 100 may include one or more sensor 101, transmitterunit 102, communication link 103, and data processing terminal 105.Moreover, within the scope of the present invention, the analytemonitoring system 100 may be a continuous monitoring system, orsemi-continuous, or a discrete monitoring system. In a multi-componentenvironment, each device is configured to be uniquely identified by eachof the other devices in the system so that communication conflict isreadily resolved between the various components within the analytemonitoring system 100.

In one embodiment of the present invention, the sensor 101 is physicallypositioned in or on the body of a user whose analyte level is beingmonitored. The sensor 101 may be configured to continuously sample theanalyte level of the user and convert the sampled analyte level into acorresponding data signal for transmission by the transmitter unit 102.In one embodiment, the transmitter unit 102 is coupled to the sensor 101so that both devices are positioned on the user's body, with at least aportion of the analyte sensor 101 positioned transcutaneously under theskin layer of the user. The transmitter unit 102 performs dataprocessing such as filtering and encoding on data signals, each of whichcorresponds to a sampled analyte level of the user, for transmission tothe primary receiver unit 104 via the communication link 103.

In one embodiment, the analyte monitoring system 100 is configured as aone-way RF communication path from the transmitter unit 102 to theprimary receiver unit 104. In such embodiment, the transmitter unit 102transmits the sampled data signals received from the sensor 101 withoutacknowledgement from the primary receiver unit 104 that the transmittedsampled data signals have been received. For example, the transmitterunit 102 may be configured to transmit the encoded sampled data signalsat a fixed rate (e.g., at one minute intervals) after the completion ofthe initial power on procedure. Likewise, the primary receiver unit 104may be configured to detect such transmitted encoded sampled datasignals at predetermined time intervals. Alternatively, the analytemonitoring system 100 may be configured with a bi-directional RF (orotherwise) communication between the transmitter unit 102 and theprimary receiver unit 104.

Additionally, in one aspect, the primary receiver unit 104 may includetwo sections. The first section is an analog interface section that isconfigured to communicate with the transmitter unit 102 via thecommunication link 103. In one embodiment, the analog interface sectionmay include an RF receiver and an antenna for receiving and amplifyingthe data signals from the transmitter unit 102, which are thereafter,demodulated with a local oscillator and filtered through a band-passfilter. The second section of the primary receiver unit 104 is a dataprocessing section which is configured to process the data signalsreceived from the transmitter unit 102 such as by performing datadecoding, error detection and correction, data clock generation, anddata bit recovery.

In operation, upon completing the power-on procedure, the primaryreceiver unit 104 is configured to detect the presence of thetransmitter unit 102 within its range based on, for example, thestrength of the detected data signals received from the transmitter unit102 or a predetermined transmitter identification information. Uponsuccessful synchronization with the corresponding transmitter unit 102,the primary receiver unit 104 is configured to begin receiving from thetransmitter unit 102 data signals corresponding to the user's detectedanalyte level. More specifically, the primary receiver unit 104 in oneembodiment is configured to perform synchronized time hopping with thecorresponding synchronized transmitter unit 102 via the communicationlink 103 to obtain the user's detected analyte level.

Referring again to FIG. 1, the data processing terminal 105 may includea personal computer, a portable computer such as a laptop or a handhelddevice (e.g., personal digital assistants (PDAs)), and the like, each ofwhich may be configured for data communication with the receiver via awired or a wireless connection. Additionally, the data processingterminal 105 may further be connected to a data network (not shown) forstoring, retrieving and updating data corresponding to the detectedanalyte level of the user.

Within the scope of the present invention, the data processing terminal105 may include an infusion device such as an insulin infusion pump orthe like, which may be configured to administer insulin to patients, andwhich may be configured to communicate with the receiver unit 104 forreceiving, among others, the measured analyte level. Alternatively, thereceiver unit 104 may be configured to integrate an infusion devicetherein so that the receiver unit 104 is configured to administerinsulin therapy to patients, for example, for administering andmodifying basal profiles, as well as for determining appropriate bolusesfor administration based on, among others, the detected analyte levelsreceived from the transmitter unit 102.

Additionally, the transmitter unit 102, the primary receiver unit 104and the data processing terminal 105 may each be configured forbi-directional wireless communication such that each of the transmitterunit 102, the primary receiver unit 104 and the data processing terminal105 may be configured to communicate (that is, transmit data to andreceive data from) with each other via the wireless communication link.More specifically, the data processing terminal 105 may in oneembodiment be configured to receive data directly from the transmitterunit 102 via the communication link, where the communication link, asdescribed above, may be configured for bi-directional communication.

In this embodiment, the data processing terminal 105 which may includean insulin pump, may be configured to receive the analyte signals fromthe transmitter unit 102, and thus, incorporate the functions of thereceiver unit 104 including data processing for managing the patient'sinsulin therapy and analyte monitoring. In one embodiment, thecommunication link 103 may include one or more of an RF communicationprotocol, an infrared communication protocol, a Bluetooth® enabledcommunication protocol, an 802.11x wireless communication protocol, oran equivalent wireless communication protocol which would allow secure,wireless communication of several units (for example, per HIPAArequirements) while avoiding potential data collision and interference.

FIG. 2 is a block diagram of the transmitter of the data monitoring anddetection system shown in FIG. 1 in accordance with one embodiment ofthe present invention. Referring to the Figure, the transmitter unit 102in one embodiment includes an analog interface 201 configured tocommunicate with the sensor 101 (FIG. 1), a user input 202, and atemperature detection section 203, each of which is operatively coupledto a transmitter processor 204 such as a central processing unit (CPU).As can be seen from FIG. 2, there are provided four contacts, three ofwhich are electrodes—work electrode (W) 210, guard contact (G) 211,reference electrode (R) 212, and counter electrode (C) 213, eachoperatively coupled to the analog interface 201 of the transmitter unit102 for connection to the sensor 101 (FIG. 1). In one embodiment, eachof the work electrode (W) 210, guard contact (G) 211, referenceelectrode (R) 212, and counter electrode (C) 213 may be made using aconductive material that is either printed or etched, for example, suchas carbon which may be printed, or metal foil (e.g., gold) which may beetched. Moreover, in a further aspect, the electrode layers may bedisposed in a stacked configuration where, each of the working electrode210, the reference electrode 212 and the counter electrode 213 may bedisposed on a substrate layer with one or more dielectric layersdisposed therebetween such that at least a portion of each of theelectrodes are positioned on top of one another in a stacked or layeredconfiguration.

Further shown in FIG. 2 are a transmitter serial communication section205 and an RF transmitter 206, each of which is also operatively coupledto the transmitter processor 204. Moreover, a power supply 207 such as abattery is also provided in the transmitter unit 102 to provide thenecessary power for the transmitter unit 102. Additionally, as can beseen from the Figure, clock 208 is provided to, among others, supplyreal time information to the transmitter processor 204.

In one embodiment, a unidirectional input path is established from thesensor 101 (FIG. 1) and/or manufacturing and testing equipment to theanalog interface 201 of the transmitter unit 102, while a unidirectionaloutput is established from the output of the RF transmitter 206 of thetransmitter unit 102 for transmission to the primary receiver unit 104.In this manner, a data path is shown in FIG. 2 between theaforementioned unidirectional input and output via a dedicated link 209from the analog interface 201 to serial communication section 205,thereafter to the processor 204, and then to the RF transmitter 206. Assuch, in one embodiment, via the data path described above, thetransmitter unit 102 is configured to transmit to the primary receiverunit 104 (FIG. 1), via the communication link 103 (FIG. 1), processedand encoded data signals received from the sensor 101 (FIG. 1).Additionally, the unidirectional communication data path between theanalog interface 201 and the RF transmitter 206 discussed above allowsfor the configuration of the transmitter unit 102 for operation uponcompletion of the manufacturing process as well as for directcommunication for diagnostic and testing purposes.

As discussed above, the transmitter processor 204 is configured totransmit control signals to the various sections of the transmitter unit102 during the operation of the transmitter unit 102. In one embodiment,the transmitter processor 204 also includes a memory (not shown) forstoring data such as the identification information for the transmitterunit 102, as well as the data signals received from the sensor 101. Thestored information may be retrieved and processed for transmission tothe primary receiver unit 104 under the control of the transmitterprocessor 204. Furthermore, the power supply 207 may include acommercially available battery.

The transmitter unit 102 is also configured such that the power supplysection 207 is capable of providing power to the transmitter for aminimum of about three months of continuous operation after having beenstored for about eighteen months in a low-power (non-operating) mode. Inone embodiment, this may be achieved by the transmitter processor 204operating in low power modes in the non-operating state, for example,drawing no more than approximately 1 μA of current. Indeed, in oneembodiment, the final step during the manufacturing process of thetransmitter unit 102 may place the transmitter unit 102 in the lowerpower, non-operating state (i.e., post-manufacture sleep mode). In thismanner, the shelf life of the transmitter unit 102 may be significantlyimproved. Moreover, as shown in FIG. 2, while the power supply unit 207is shown as coupled to the processor 204, and as such, the processor 204is configured to provide control of the power supply unit 207, it shouldbe noted that within the scope of the present invention, the powersupply unit 207 is configured to provide the necessary power to each ofthe components of the transmitter unit 102 shown in FIG. 2.

Referring back to FIG. 2, the power supply section 207 of thetransmitter unit 102 in one embodiment may include a rechargeablebattery unit that may be recharged by a separate power supply rechargingunit (for example, provided in the receiver unit 104) so that thetransmitter unit 102 may be powered for a longer period of usage time.Moreover, in one embodiment, the transmitter unit 102 may be configuredwithout a battery in the power supply section 207, in which case thetransmitter unit 102 may be configured to receive power from an externalpower supply source (for example, a battery) as discussed in furtherdetail below.

Referring yet again to FIG. 2, the temperature detection section 203 ofthe transmitter unit 102 is configured to monitor the temperature of theskin near the sensor insertion site. The temperature reading is used toadjust the analyte readings obtained from the analog interface 201. TheRF transmitter 206 of the transmitter unit 102 may be configured foroperation in the frequency band of 315 MHz to 322 MHz, for example, inthe United States. Further, in one embodiment, the RF transmitter 206 isconfigured to modulate the carrier frequency by performing FrequencyShift Keying and Manchester encoding. In one embodiment, the datatransmission rate is 19,200 symbols per second, with a minimumtransmission range for communication with the primary receiver unit 104.

Referring yet again to FIG. 2, also shown is a leak detection circuit214 coupled to the guard contact (G) 211 and the processor 204 in thetransmitter unit 102 of the data monitoring and management system 100.The leak detection circuit 214 in accordance with one embodiment of thepresent invention may be configured to detect leakage current in thesensor 101 to determine whether the measured sensor data are corrupt orwhether the measured data from the sensor 101 is accurate.

Additional detailed description of the continuous analyte monitoringsystem, its various components including the functional descriptions ofthe transmitter are provided in U.S. Pat. No. 6,175,752 issued Jan. 16,2001 entitled “Analyte Monitoring Device and Methods of Use”, and inU.S. patent application Ser. No. 10/745,878 filed Dec. 26, 2003, nowU.S. Pat. No. 7,811,231, entitled “Continuous Glucose Monitoring Systemand Methods of Use”, each assigned to the Assignee of the presentapplication, the disclosure of each of which are incorporated herein byreference for all purposes.

FIG. 3 is a block diagram of the receiver/monitor unit of the datamonitoring and management system shown in FIG. 1 in accordance with oneembodiment of the present invention. Referring to FIG. 3, the primaryreceiver unit 104 includes a blood glucose test strip interface 301, anRF receiver 302, an input 303, a temperature detection section 304, anda clock 305, each of which is operatively coupled to a receiverprocessor 307. As can be further seen from the Figure, the primaryreceiver unit 104 also includes a power supply 306 operatively coupledto a power conversion and monitoring section 308. Further, the powerconversion and monitoring section 308 is also coupled to the receiverprocessor 307. Moreover, also shown are a receiver serial communicationsection 309, and an output 310, each operatively coupled to the receiverprocessor 307.

In one embodiment, the test strip interface 301 includes a glucose leveltesting portion to receive a manual insertion of a glucose test strip,and thereby determine and display the glucose level of the test strip onthe output 310 of the primary receiver unit 104. This manual testing ofglucose can be used to calibrate sensor 101. The RF receiver 302 isconfigured to communicate, via the communication link 103 (FIG. 1) withthe RF transmitter 206 of the transmitter unit 102, to receive encodeddata signals from the transmitter unit 102 for, among others, signalmixing, demodulation, and other data processing. The input 303 of theprimary receiver unit 104 is configured to allow the user to enterinformation into the primary receiver unit 104 as needed. In one aspect,the input 303 may include one or more keys of a keypad, atouch-sensitive screen, or a voice-activated input command unit. Thetemperature detection section 304 is configured to provide temperatureinformation of the primary receiver unit 104 to the receiver processor307, while the clock 305 provides, among others, real time informationto the receiver processor 307.

Each of the various components of the primary receiver unit 104 shown inFIG. 3 is powered by the power supply 306 which, in one embodiment,includes a battery. Furthermore, the power conversion and monitoringsection 308 is configured to monitor the power usage by the variouscomponents in the primary receiver unit 104 for effective powermanagement and to alert the user, for example, in the event of powerusage which renders the primary receiver unit 104 in sub-optimaloperating conditions. An example of such sub-optimal operating conditionmay include, for example, operating the vibration output mode (asdiscussed below) for a period of time thus substantially draining thepower supply 306 while the processor 307 (thus, the primary receiverunit 104) is turned on. Moreover, the power conversion and monitoringsection 308 may additionally be configured to include a reverse polarityprotection circuit such as a field effect transistor (FET) configured asa battery activated switch.

The serial communication section 309 in the primary receiver unit 104 isconfigured to provide a bi-directional communication path from thetesting and/or manufacturing equipment for, among others,initialization, testing, and configuration of the primary receiver unit104. Serial communication section 309 can also be used to upload data toa computer, such as time-stamped blood glucose data. The communicationlink with an external device (not shown) can be made, for example, bycable, infrared (IR) or RF link. The output 310 of the primary receiverunit 104 is configured to provide, among others, a graphical userinterface (GUI) such as a liquid crystal display (LCD) for displayinginformation. Additionally, the output 310 may also include an integratedspeaker for outputting audible signals as well as to provide vibrationoutput as commonly found in handheld electronic devices, such as mobiletelephones presently available. In a further embodiment, the primaryreceiver unit 104 also includes an electro-luminescent lamp configuredto provide backlighting to the output 310 for output visual display indark ambient surroundings.

Referring back to FIG. 3, the primary receiver unit 104 in oneembodiment may also include a storage section such as a programmable,non-volatile memory device as part of the processor 307, or providedseparately in the primary receiver unit 104, operatively coupled to theprocessor 307. The processor 307 is further configured to performManchester decoding as well as error detection and correction upon theencoded data signals received from the transmitter unit 102 via thecommunication link 103.

In a further embodiment, the one or more of the transmitter unit 102,the primary receiver unit 104, secondary receiver unit 106, or the dataprocessing terminal/infusion section 105 may be configured to receivethe blood glucose value wirelessly over a communication link from, forexample, a glucose meter. In still a further embodiment, the user orpatient manipulating or using the analyte monitoring system 100 (FIG. 1)may manually input the blood glucose value using, for example, a userinterface (for example, a keyboard, keypad, and the like) incorporatedin the one or more of the transmitter unit 102, the primary receiverunit 104, secondary receiver unit 106, or the data processingterminal/infusion section 105.

FIG. 4 is a schematic of the dynamic multi-stage signal amplification inthe transmitter unit of the data monitoring and management system shownin FIG. 1 in accordance with one embodiment of the present invention.Referring to FIG. 4, there is provided in one embodiment atransimpedance amplifier 420 whose output terminal 423 is coupled to afirst input terminal 411 of the analog to digital converter (ADC) 410 inthe analog interface 201 (FIG. 2) of the transmitter unit 102. Furthershown in FIG. 4, the monitored analyte sensor signal from the sensor 101is provided to an inverting input terminal 421 of the transimpedanceamplifier 420. The sensor signal in FIG. 4 is shown as a signal source440. Also shown in FIG. 4 is resistor 460. Furthermore, a noninvertinginput terminal 422 of the transimpedance amplifier 420 is provided witha reference voltage signal from a reference signal source Vref 450. Inone embodiment, the reference voltage signal may be approximately 1.012volts. However, based upon the component tolerance, and designconfiguration, other suitable reference voltage signals may be used.

In one aspect, based on the input analyte sensor signal from the signalsource 440 and the reference signal Vref 450, the transimpedanceamplifier 420 may be in one embodiment configured to convert thereceived current signal representing the monitored or detected analytelevel, and to convert the current signal to a corresponding voltagesignal which is provided to the output terminal 423 of thetransimpedance amplifier 420. Further, as shown in FIG. 4 the monitoredanalyte voltage signal from the output terminal 423 of thetransimpedance amplifier 420 is provided to the first input terminal 411(Channel 1) of the ADC 410.

Referring again to FIG. 4, a second amplifier 430 is provided in oneembodiment whose noninverting input terminal 431 is coupled to theoutput terminal 423 of the transimpedance amplifier 420 to receive theoutput voltage signal corresponding to the monitored analyte level,while an inverting input terminal 432 of the second amplifier 430 iscoupled in one embodiment to the reference signal Vref source 450.Moreover, output terminal 433 of the second amplifier is coupled in oneembodiment to a second input terminal 412 (Channel 2) of the ADC 410. Inoperation, the second amplifier 430 may be configured to step up theoutput signal of the transimpedance amplifier 410 by a predeterminedfactor (for example, a factor of 2), and to provide the stepped upsignal to the analog to digital converter (ADC) 410.

Referring back to FIG. 4, the analog to digital converter (ADC) 410 ofthe analog interface 201 (FIG. 2) of the transmitter unit 102 (FIG. 1)in one embodiment may be configured to detect signals at both the firstand second input terminals or channels 411, 412, and based on one ormore predetermined process or routine, the voltage signal at one of thefirst or the second input terminals or channels 411, 412 is used by theADC 410 for further processing as corresponding to the monitored analytelevel from the sensor 101 (FIG. 1). That is, in one embodiment,depending upon the signal resolution corresponding to the analyte levelmonitored, the ADC 410 may be configured to select one of the outputsignals from the transimpedance amplifier 420 or the second amplifier430 for further processing.

For example, when the signal received at the second input terminal 412of the ADC 410 exceeds a predetermined threshold value, the input signalat the first input terminal 411 may be used. More specifically, in oneembodiment, the ADC 410 may be configured to process the signals at thesecond input terminal 412 (Channel 2) since it has a higher resolutioncompared to the signal at the first input terminal 411 received from thetransimpedance amplifier 420. When the signal received at the secondinput terminal 412 exceeds a predetermined threshold level (for example,based on the tolerance level of the analog to digital converter (ADC)410), the voltage signal received at the first input terminal 411 fromthe transimpedance amplifier 420 may be used to convert to acorresponding digital signal representing the monitored analyte leveldetected by the sensor 101 (FIG. 1).

Referring back to FIG. 4, in one embodiment, the analog to digitalconverter (ADC) 410 may include a 12 bit A/D converter configured tosupport up to approximately 4,096 bits or ADC counts. In this case, inone embodiment, when the signal at the second input terminal 412 of theADC 410 approaches approximately 4,000 bits or ADC counts, for example,the processor 204 (FIG. 2) of the transmitter unit 102 may be configuredto switch from the second input terminal 412 to the first input terminal411, to use the output signal from the transimpedance amplifier 420. Inthis manner, in one embodiment, the processor 204 of the transmitterunit 102 may be configured to monitor the signal levels at the two inputterminals 411, 412 of the ADC 410, and when the signal level or ADCcount associated with the output signal from the second amplifier 430provided at the second input terminal 412 of the ADC 410 exceeds thepredetermined threshold (for example, 4,000 bits or ADC count), theprocessor 204 may be configured to switch over to the output signal ofthe transimpedance amplifier 410 provided on the first input terminal411 of the ADC 410 for further processing.

In the manner described above, the dynamic multi-stage amplifierconfiguration in one embodiment may be configured to support variationsin the analyte sensor sensitivities due to, for example, manufacturingvariations, among others, while maintaining an acceptable or desirablesensor signal resolution. For example, in one embodiment, highsensitivity sensors may be configured for use with the full scale orrange (for example, up to approximately 150 nA corresponding to thesupported approximately 500 mg/dL glucose level) associated with thetransimpedance amplifier 420 output signal provided to the first inputterminal 411 (Channel 1) of the analog to digital converter (ADC) 410,while low sensitivity sensors may be associated with the secondamplifier 430 output signal (for example, full scale current signallevel of approximately 75 nA corresponding to the supportedapproximately 500 mg/dL glucose level) provided to the second inputterminal 412 (Channel 2) of the analog to digital converter (ADC) 410.

For example, as discussed above, in one embodiment, the processor 204 ofthe transmitter unit 102 may be configured to monitor the signals at thetwo input terminals 411, 412 of the ADC 410, and determine, that if thereceived signal level does not have sufficient resolution to convert tothe desired resolution of the digital signal (for example, 12 bits forthe ADC 410) corresponding to the monitored analyte level associatedwith the sensor 101, the processor 204 may be configured to dynamicallytoggle or switch from using the voltage signal received from one of thetwo input terminals 411, 412, to using the voltage signal from the otherone of the two input terminals 411, 412 to provide a dynamic range oftolerance level for the sensor sensitivities.

Accordingly, an apparatus in one embodiment includes a first amplifierhaving at least one input terminal and an output terminal, the at leastone input terminal coupled to a signal source, the output terminalconfigured to provide a first output signal, a second amplifier havingat least one input terminal and an output terminal, the at least oneinput terminal coupled to the output terminal of the first amplifier,the output terminal of the second amplifier configured to provide asecond output signal, a processor operatively coupled to receive thefirst output signal and the second output signal, where the first outputsignal is a predetermined ratio of the second output signal, andfurther, where the first output signal and the second output signal areassociated with a monitored analyte level of a user.

In one aspect, the first amplifier may include a transimpedanceamplifier.

The monitored analyte level may include glucose level.

Also, the at least one input terminal of the first amplifier may includean inverting input terminal, and, also may include a reference signalsource coupled to a noninverting input terminal of the first amplifier.

In a further aspect, the second amplifier may include a gain ofapproximately two.

In still another aspect, the first output signal may be associated witha signal level from the signal source.

The apparatus may also include an analog to digital converter coupled tothe output terminals of the first and second amplifiers, where theanalog to digital (A/D) converter may include a 12 bit A/D converter.

The apparatus in another embodiment may include a processor operativelycoupled to the A/D converter for processing the one or more signalsreceived at the one or more first amplifier output terminal and thesecond amplifier output terminal.

Moreover, the processor may be configured to compare the one or moresignals received at the one or more first amplifier output terminal andthe second amplifier output terminal to a predetermined threshold value,which, in one embodiment may include approximately 4,000 bits (or analogto digital converter (ADC) counts).

Still further, the processor may be configured to process a signalassociated with one of the one or more signals received at the one ormore first amplifier output terminal and the second amplifier outputterminal when another signal associated with the other one of the one ormore signals received at the one or more first amplifier output terminaland the second amplifier output terminal exceeds the predeterminedthreshold value.

A method in accordance with another embodiment includes receiving afirst signal having a first signal resolution and associated with amonitored analyte level of a user, receiving a second signal having asecond signal resolution and associated with the monitored analyte levelof the user, comparing the received first signal to a predeterminedthreshold level, and processing one of the received first or secondsignals based on the comparing step.

When the received first signal does not exceed the predeterminedthreshold level, further including processing the first signal. On theother hand, when the received first signal exceeds the predeterminedthreshold level, further including processing the second signal.

A data processing device in accordance with still another embodimentincludes a multi stage amplifier unit configured to receive a signal andto generate a plurality of amplifier unit output signals eachcorresponding to a monitored analyte level of a patient, an analog todigital (A/D) conversion unit operatively coupled to the multi-stageamplifier unit configured to digitally convert the plurality ofamplifier unit output signals, and a processor unit operatively coupledto the A/D conversion unit, the processor unit configured to process oneof the plurality of digitally converted amplifier unit output signals.

The device in another aspect may include a data communication unitoperatively coupled to the processor unit, and configured to transmitthe digitally converted and processed amplifier unit output signal.

The data communication unit may include an RF transmitter for wirelessdata transmission to a remote device such as, for example, a datareceiver unit, data processing terminal, an infusion device or the likeconfigured for RF communication.

Various other modifications and alterations in the structure and methodof operation of this invention will be apparent to those skilled in theart without departing from the scope and spirit of the invention.Although the invention has been described in connection with specificpreferred embodiments, it should be understood that the invention asclaimed should not be unduly limited to such specific embodiments. It isintended that the following claims define the scope of the presentinvention and that structures and methods within the scope of theseclaims and their equivalents be covered thereby.

What is claimed is:
 1. A method of processing signals from an analytesensor, comprising: coupling a first amplifier to a second amplifier anda signal source; determining that a first signal at an output terminalof the second amplifier exceeds a converter tolerance value; andprocessing a second signal at the output terminal of the secondamplifier when the first signal at the output terminal of the secondamplifier exceeds the converter tolerance value.
 2. The method of claim1, wherein the first amplifier comprises a transimpedance amplifier. 3.The method of claim 2, wherein the transimpedance amplifier is coupledto an analog to digital converter, and wherein the converter tolerancevalue corresponds to a tolerance level of the analog to digitalconverter.
 4. The method of claim 1, wherein the first amplifier has ahigher resolution than the second amplifier.
 5. The method of claim 1,wherein the first signal and the second signal are from an in vivoanalyte sensor.
 6. The method of claim 5, wherein the in vivo analytesensor comprises a plurality of electrodes including a working electrodecomprising an analyte-responsive enzyme bonded to a polymer disposed onthe working electrode.
 7. The method of claim 6, wherein theanalyte-responsive enzyme is chemically bonded to the polymer.
 8. Themethod of claim 6, wherein the working electrode further comprises amediator.
 9. The method of claim 5, wherein the in vivo analyte sensorcomprises a plurality of electrodes including a working electrodecomprising a mediator bonded to a polymer disposed on the workingelectrode.
 10. The method of claim 9, wherein the mediator is chemicallybonded to the polymer.
 11. An apparatus, comprising: a first amplifieroperatively coupled to a signal source; a second amplifier operativelycoupled to the first amplifier, the second amplifier comprising anoutput terminal; and a processing unit operatively coupled to one ormore of the first amplifier and the second amplifier, the processingunit configured to: determine that a first signal at the output terminalof the second amplifier exceeds a converter tolerance value; and processa second signal at the output terminal of the second amplifier when thefirst signal at the output terminal of the second amplifier exceeds theconverter tolerance value.
 12. The apparatus of claim 11, wherein thefirst amplifier comprises a transimpedance amplifier.
 13. The apparatusof claim 12, wherein the transimpedance amplifier is coupled to ananalog to digital converter, and wherein the converter tolerance valuecorresponds to a tolerance level of the analog to digital converter. 14.The apparatus of claim 11, wherein the first amplifier has a higherresolution than the second amplifier.
 15. The apparatus of claim 11,wherein the first signal and the second signal are sensor signals froman in vivo analyte sensor.
 16. The apparatus of claim 15, wherein the invivo analyte sensor comprises a plurality of electrodes including aworking electrode comprising an analyte-responsive enzyme bonded to apolymer disposed on the working electrode.
 17. The apparatus of claim16, wherein the analyte-responsive enzyme is chemically bonded to thepolymer.
 18. The apparatus of claim 16, wherein the working electrodefurther comprises a mediator.
 19. The apparatus of claim 15, wherein thein vivo analyte sensor comprises a plurality of electrodes including aworking electrode comprising a mediator bonded to a polymer disposed onthe working electrode.
 20. The apparatus of claim 19, wherein themediator is chemically bonded to the polymer.